Require Import String.

(* https://docs.python.org/3/library/string.html#formatspec *)

(* bcdeEfFgGnosxX% *)
Inductive type: Set := | TypHex | TypInt | TypStr | TypFloat.

Inductive align: Set := AlignLeft | AlignRight | AlignJust | AlignCenter.
Inductive sign: Set := SignPos | SignNeg | SignSpc.

Definition digit := nat.
Definition width := digit.
Definition precision := digit.

Inductive prec :=
| Prec: width -> option type -> prec.

Notation "'․' width '_d'" := (Prec width (Some TypInt))
  (at level 9, width constr).
Notation "'․' width" := (Prec width None) (at level 10).


Print Grammar constr.
Compute ․2.
Compute ․2 _d.


Inductive spec: Set :=
| Spec: option width -> precision -> type -> spec.

(* .2f *)
Check Spec None 2 TypFloat. 

Notation "F '.' precision typ " := (Spec None precision typ) (at level 50).
Check F.2


(*
Inductive digit: Set := | D0 | D1 | D2 | D3 | D4 | D5 | D6 | D7 | D8 | D9.

Inductive align: Type := option Ascii.ascii -> 

Inductive spec: Type :=
| Spec: align -> 
 *)